US4451805A - Surface acoustic wave filter - Google Patents

Surface acoustic wave filter Download PDF

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Publication number
US4451805A
US4451805A US06/371,502 US37150282A US4451805A US 4451805 A US4451805 A US 4451805A US 37150282 A US37150282 A US 37150282A US 4451805 A US4451805 A US 4451805A
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US
United States
Prior art keywords
surface acoustic
acoustic wave
photoconductive
output transducers
wave filter
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US06/371,502
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English (en)
Inventor
Masaaki Ono
Yoshiro Fujiwara
Masanobu Yanagisawa
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Fujitsu Ltd
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Fujitsu Ltd
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Assigned to FUJITSU LIMITED 1015 KAMIKODANAKA, NAKAHARA-KU, KAWASAKI-SHI, KANAGAWA 211, JAPAN A CORP OF JAPAN reassignment FUJITSU LIMITED 1015 KAMIKODANAKA, NAKAHARA-KU, KAWASAKI-SHI, KANAGAWA 211, JAPAN A CORP OF JAPAN ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: FUJIWARA, YOSHIRO, ONO, MASAAKI, YANAGISAWA, MASANOBU
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/70—Multiple-port networks for connecting several sources or loads, working on different frequencies or frequency bands, to a common load or source
    • H03H9/72—Networks using surface acoustic waves
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02535—Details of surface acoustic wave devices
    • H03H9/0296—Surface acoustic wave [SAW] devices having both acoustic and non-acoustic properties
    • H03H9/02968—Surface acoustic wave [SAW] devices having both acoustic and non-acoustic properties with optical devices
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/64—Filters using surface acoustic waves
    • H03H9/6403—Programmable filters
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/64—Filters using surface acoustic waves
    • H03H9/6423—Means for obtaining a particular transfer characteristic
    • H03H9/643—Means for obtaining a particular transfer characteristic the transfer characteristic being determined by reflective or coupling array characteristics
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic elements; Electromechanical resonators
    • H03H9/74—Multiple-port networks for connecting several sources or loads, working on the same frequency or frequency band, to a common load or source
    • H03H9/76—Networks using surface acoustic waves

Definitions

  • the present invention relates to improvements in a surface acoustic wave filter.
  • FIG. 1 A prior art surface acoustic wave filter is illustrated in FIG. 1.
  • This surface acoustic wave filter comprises: a substrate 1 of a piezoelectric material such as lithium niobate (LiNbO 3 ) or lithium tantalate (LiTaO 3 ); a multistrip coupler 2 comprising a plurality of parallel conductive strips formed on the substrate; an input transducer 3 disposed on one side of the multistrip coupler 2; and two output transducers 4 and 5 disposed on the other side of the multistrip coupler 2.
  • a piezoelectric material such as lithium niobate (LiNbO 3 ) or lithium tantalate (LiTaO 3 )
  • a multistrip coupler 2 comprising a plurality of parallel conductive strips formed on the substrate
  • an input transducer 3 disposed on one side of the multistrip coupler 2
  • two output transducers 4 and 5 disposed on the other side of the multistrip coupler
  • Electric wave signals introduced from a source 6 to the input transducer 3 are converted to surface acoustic wave signals and transmitted to the output transducers 4 and 5 through the multistrip coupler 2.
  • the transmitted surface acoustic wave signals are reconverted to electric wave signals by each of the output transducers 4 and 5 and transmitted to output terminals 7.
  • Each of the input and output transducers 3, 4, 5 has a filtering characteristic which is determined by the shape of the electrodes thereof. Only signals of a frequency corresponding to the filtering characteristic can pass through each transducer when changing from electric signals to acoustic wave signals, or vice versa.
  • Input power from the input transducer 3 is distributed to the output transducers 4 and 5 by the multistrip coupler 2.
  • the distribution ratio changes cyclically in accordance with the change of the number of conductive strips of the multistrip coupler 2, as shown in FIG. 2.
  • the abscissa represents the number of strips of the multistrip coupler and the ordinate represents the output power of each output transducer.
  • the solid line P 1 represents the output power of the output transducer 4.
  • the dotted line P 2 represents the output power of the other output transducer 5.
  • the number of strips of the multistrip coupler 2 cannot be changed after the multistrip coupler 2 is once formed on the substrate. Therefore, the distribution ratio of the input power to the two output transducers 4 and 5 is nonadjustable in the multistrip coupler of the surface acoustic wave filter of the prior art.
  • An object of this invention is to provide a multistrip coupler for controlling the distribution of signal power transmitted to selected output transducers. Another object of the invention is to provide a portion of each of the conductive strips of the multistrip coupler with a photoconductive material.
  • a surface acoustic wave filter according to the present invention comprises: a substrate of piezoelectric material; a multistrip coupler comprising a plurality of parallel conductive strips formed on the substrate; at least one input transducer disposed on one side of the multistrip coupler, and at least one output transducer disposed on the other side of the multistrip coupler.
  • the surface acoustic wave filter of the present invention is characterized in that a part of the middle portion of each of the conductive strips of the multistrip coupler is made of a photoconductive material.
  • FIG. 1 is a plan view of a prior art surface acoustic wave filter
  • FIG. 2 is a graph of the power distribution to the two output transducers through the multistrip coupler
  • FIG. 3 is a plan view of a surface acoustic wave filter of the present invention.
  • FIG. 4 is an equivalent circuit diagram of the multistrip coupler of the surface acoustic wave filter of FIG. 3;
  • FIG. 5 is a graph of the filtering characteristics of bands of different widths to be filtered
  • FIG. 6 is a graph of the filtering characteristics of different frequencies to be filtered
  • FIG. 7 is a plan view of a second embodiment of the present invention.
  • FIG. 8 is a graph of the filtering characteristics of the output transducers illustrated in FIG. 7;
  • FIG. 9 is a graph of the delay characteristics of the output transducers illustrated in FIG. 7;
  • FIG. 10 is a plan view of a third embodiment of the present invention.
  • FIG. 11 is a graph of the filtering characteristics of the output transducers illustrated in FIG. 10.
  • FIG. 3 An embodiment of the present invention is illustrated in FIG. 3.
  • the surface acoustic wave filter illustrated in FIG. 3 comprises a substrate 8 of a piezoelectric material, a multistrip coupler 9, an input transducer 10 disposed on one side of the multistrip coupler 9, and two output transducers 11 and 12 disposed on the other side of the multistrip coupler 9.
  • the central hatched portion 13 of each conductive strip of the multistrip coupler 9 is made of a photoconductive material such as cadmium-selenium (CdSe).
  • the photoconductive portion 13 serves as a conductor when it is lighted and serves as an insulator when it is not lighted.
  • R represents the resistance of the photoconductive portion
  • r represents the impedance of the multistrip coupler, in which Rl ⁇ r ⁇ Rd (Rl ⁇ 0).
  • the surface acoustic wave filter according to the present invention comprises a multistrip coupler having strips, each of which has a photoconductive portion. Therefore it is possible to change and adjust the distribution of signal power transmitted to the output tranducers. Also, it is possible to enlarge the field of application of the surface acoustic wave filter.
  • the desired amount of signal can be transmitted to each of the output transducers by selectively lighting the strips of the multistrip coupler.
  • the photoconductive portions of the surface acoustic wave filter of the present invention can be used as a switch for selecting output transducers thereof by lighting all the photoconductive portions simultaneously.
  • the number of strips of the multistrip coupler is preset so that all of the signal power from the input transducer 10 is transmitted to the output transducer 12 when all of the photoconductive portions are lighted, while all of the signal power from the input transducer 10 is transmitted to the other output transducer 11 when none of the photoconductive portions are lighted.
  • the output transducers 11 and 12 may have different filtering characteristics A and B, respectively, as illustrated in FIG. 5.
  • the characteristic A has a wider filtering band than the characteristic B.
  • signals from the input transducer 10 are first transmitted to the output transducer 11 which passes A wide range of signals for rough signal treatment. Then, the photoconductive portions 13 are lighted to change the effective output transducer from 11 to 12 which passes a narrow range of signals for precise signal adjustment.
  • the output transducers 11 and 12 may also have completely different filtering characteristics A and B, respectively, as illustrated in FIG. 6, so that of the output transducers 11, 12 passes a different frequency band of signals.
  • the photoconductive portions are used as a switch for changing the signal channel.
  • the surface acoustic wave filter may comprise only one output transducer 12. In this case, the entire group of the photoconductive portions 13 is used as a switch for turning on or off the output transducer 12.
  • FIG. 7 Another embodiment of the present invention is illustrated in FIG. 7.
  • Horizontal distances l 1 and l 2 in the drawing between the input transducer 10 and the output transducers 11 and 12 differ from each other.
  • the transmission time of signals from the input transducer 10 to the output transducer 11 is more than the transmission time from the input transducer 10 to the output transducer 12, as can be seen from FIG. 9, which illustrates the delay characteristics A', B', of the output transducers 11 and 12.
  • both output transducers 11 and 12 may have the same filtering characteristic A, B, as illustrated in FIG. 8.
  • On of the output transducers 11 or 12 can be selectively used by lighting or not lighting the photoconductive portions 13.
  • FIG. 10 A further embodiment of the present invention is illustrated in FIG. 10.
  • Three output transducers 11, 12 and 14 are disposed side by side facing the multistrip coupler 9.
  • the output transducers 11, 12 and 14 have different filtering characteristics A, B and C, respectively, as illustrated in FIG. 11.
  • Two portions 13a and 13b of each strip of the multistrip coupler 9 are made of a photoconductive material.
  • the photoconductive portions 13a and 13b are located at the positions which correspond to the spaces between two adjacent output transducers.
  • the output tranducer 11 can be selected by lighting the portions 13a and not lighting the portion 13b.
  • the output transducer 12 can be selected by not lighting the portions 13a and 13b.
  • the output transducer 14 can be selected by not lighting the portions 13a and lighting the portions 13b.

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
US06/371,502 1981-04-28 1982-04-23 Surface acoustic wave filter Expired - Lifetime US4451805A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP1981060654U JPS57173416U (enrdf_load_stackoverflow) 1981-04-28 1981-04-28
JP56-60654[U] 1981-04-28

Publications (1)

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US4451805A true US4451805A (en) 1984-05-29

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US06/371,502 Expired - Lifetime US4451805A (en) 1981-04-28 1982-04-23 Surface acoustic wave filter

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US (1) US4451805A (enrdf_load_stackoverflow)
EP (1) EP0064382A3 (enrdf_load_stackoverflow)
JP (1) JPS57173416U (enrdf_load_stackoverflow)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4586077A (en) * 1984-06-06 1986-04-29 Westinghouse Electric Corp. Switched surface acoustic wave apparatus for controlling cable television services
US4697115A (en) * 1984-10-15 1987-09-29 Clarion Co., Ltd. Surface acoustic wave device
US4748364A (en) * 1984-10-15 1988-05-31 Clarion Co., Ltd. Surface acoustic wave device
US20060033039A1 (en) * 2004-08-12 2006-02-16 Williams John R Photo-controlled luminescence sensor system
US20130106531A1 (en) * 2011-10-28 2013-05-02 Commissariat A L'energie Atomique Et Aux Energies Alternatives Acoustic Wave Power Device

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3446974A (en) * 1966-11-07 1969-05-27 Zenith Radio Corp Solid state acoustic signal translating device with light activated electrode interconnections
US3706055A (en) * 1970-08-27 1972-12-12 Thomson Csf Electromechanical delay with continuously adjustable delay
FR2239810A1 (enrdf_load_stackoverflow) * 1973-08-02 1975-02-28 Thomson Csf
US3911381A (en) * 1974-09-06 1975-10-07 Trw Inc Tunable acoustic wave propagation device

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3446974A (en) * 1966-11-07 1969-05-27 Zenith Radio Corp Solid state acoustic signal translating device with light activated electrode interconnections
US3706055A (en) * 1970-08-27 1972-12-12 Thomson Csf Electromechanical delay with continuously adjustable delay
FR2239810A1 (enrdf_load_stackoverflow) * 1973-08-02 1975-02-28 Thomson Csf
US3911381A (en) * 1974-09-06 1975-10-07 Trw Inc Tunable acoustic wave propagation device

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
Crowley et al., "Acoustoelectrically Controlled Saw Divider", 1977 Ultrasonics Symposium Proceedings, IEEE Cat. 77CH1264-1SU, Oct. 1977, Phoenix, Az.; pp. 633-636.
Crowley et al., Acoustoelectrically Controlled Saw Divider , 1977 Ultrasonics Symposium Proceedings, IEEE Cat. 77CH1264 1SU, Oct. 1977, Phoenix, Az.; pp. 633 636. *
Patent Abstracts of Japan, vol. 2, No. 55, Apr. 21, 1978, p. 1303. *
Patent Abstracts of Japan, vol. 2, No. 58, Apr. 26, 1978, p. 1675. *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4586077A (en) * 1984-06-06 1986-04-29 Westinghouse Electric Corp. Switched surface acoustic wave apparatus for controlling cable television services
US4697115A (en) * 1984-10-15 1987-09-29 Clarion Co., Ltd. Surface acoustic wave device
US4748364A (en) * 1984-10-15 1988-05-31 Clarion Co., Ltd. Surface acoustic wave device
US20060033039A1 (en) * 2004-08-12 2006-02-16 Williams John R Photo-controlled luminescence sensor system
US20130106531A1 (en) * 2011-10-28 2013-05-02 Commissariat A L'energie Atomique Et Aux Energies Alternatives Acoustic Wave Power Device
US8907741B2 (en) * 2011-10-28 2014-12-09 Commissariat A L'energie Atomique Et Aux Energies Alternatives Acoustic wave power device

Also Published As

Publication number Publication date
EP0064382A2 (en) 1982-11-10
JPS57173416U (enrdf_load_stackoverflow) 1982-11-01
EP0064382A3 (en) 1983-06-01

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